Stripping dyed textile



Patented July 2, 1940 UNITED STATES PATENT OFFICE STRIPPING DYED TEXTILENo Drawing. Application May 19, 1939, Serial No. 274,496

4 Claims.

This invention relates to a process for stripping dyed textile fiber,both of vegetable and of animal origin, the present application being acontinuation-in-part of my copending application 5 Ser. No. 173,848,filed November 10, 1937 (Patent No. 2,164,930, issued July 4, 1939).

It is an object of this invention to provide a novel process ofstripping which may be applied either to vegetable fiber, for instancecotton, or to 0 animal fiber such as wool and silk, without undulytendering the fiber. It is a further object of my invention to provide anovel stripping process which may be used effectively on materials dyedwith vat, direct, acid, or other azoic colors. Other and furtherimportant objects of this invention will appear as the descriptionproceeds. Stripping has been defined by some authorities as the removalor lightening of the shade or tone of a previously applied dye fromtextile material, otherwise than by extraction with solvents. Thisprocess is generally used in the arts either for the purpose ofcorrecting an overdyed shade or for obtaining a lighter colored bottomfor the redyeing of another color. It is also used largely in therecovery of wool from waste for the purpose of producing shoddy or forstripping of rags for paper manufacture. The methods employed heretoforeinvolved the use of aqueous baths of various stripping agents, accordingto the material treated or nature of dye to be removed. Among thevarious reagents employed heretofore have been ammonium hydroxide, sodaash, soap, potassium bichromate with sulfuric acid, sodium hydrosulfitewith or without acetic acid, stannous chloride with hydrochloric acid,and potassium permanganate with sulfuric acid.

Now according to my present invention, I accomplish strippingeffectively by the use of formamidine-sulfinic acid preferably from analkaline aqueous bath. Formamidine-sulfinic acid is a compoundobtainable by the oxidation of thiourea with hydrogen peroxide. It wasfirst prepared and described by Barnett in Jour. Chem. Soc.,

vol. 97, at pages 63-65 (1910). A commercially practical method for itsproduction has recent y been published by Emeric Havas in U. S. PatentNo. 2,150,921.

The mode of procedure according to my novel process involves simplytreatment of the dyed fabric in a hot aqueous solution offormamidinesulfinic acid of about 0.1 to 1% strength, and enough alkalito give the bath an alkaline reaction. Wetting or penetrating agents maybe added if desired. The quaternary ammonium compounds mentioned in U.S. Patents Nos. 2,003,928 and 2,019,124 are particularly recommended.

Without limiting my invention to any particular procedure, the followingexamples are given to illustrate my preferred mode of operation. Partsmentioned are by weight.

- Example 1 50 parts of cotton, linen, rayon or mixtures of these, inthe form of cloth or yarn, previously colored with vat dyes are treatedin 1000 parts of water containing:

Cetyl trimethyl ammonium bromide,

with or without oleic acid (See U. S. P. Parts Nos. 2,003,928 and2,019,124) 0.25 to5 Caustic soda 1.5 to3 Formamidine-sulfinic acid 1 to5The above materials may be added to the bath either before or afterentry of the textile material. In either event, the bath is heated to atemperature of 120 to 140 F. at the beginning of the treatment, and isthen gradually raised in temperature to at least 200 F., and preferably212 F., the treatment being continued with suitable agitation of thematerial for from 30 to minutes. The source of heat is then removed, andcold water is run in, permitting the excess to flow away through anysuitable arrangement, until all of the original liquor has beendisplaced. This water is then drained and 1000 parts of a /2 Tw.solution of sodium hypochlorite is added, and the material is treated init at a temperature between and F. for 20 to 30 minutes. This isfollowed by the usual rinsing in cold water, or treatment in coldsolutions of sodium thiosulfate or of other suitable substances toremove the residual hypochlorite. This treatment will remove some or allof the color, depending upon the dye or dyes and their quantity that thematerial originally contained. Among the vat dyes that are completely ornearly completely removed by this treatment are Anthrafiavone GC (C. I.1095) Caledon Brown R (C. I. 1151) Ponsol Blue GD (C. I. 1113) CaledonOlive (see C. I. Supplement page 30)6,61-iiethoxy-2,2-bisthionaphthen-indigo (C. I.

Among those less completely removed by this treatment are Ponsol DarkBlue BOA (o. I. 1099) Ponsol Blue Green FIE'B (C. I. 1173) Ponsol JadeGreen (C. I. 1101) In a similar manner azoic dyes may be removed fromcellulosic fiber, the procedure being the same as in the aforegoingexample. Among the various azo dyes which are completely or nearlycompletely removed by this treatment may be mentioned5-nitro-2-aminoanisol 2,3 hydroxynaphthoicacid-anilide o-toluidide of2,3-hydroxynaphthoic acid 4-chlor-2-nitroaniline- 2-naphthylamide of2,3-

hydroxynaphthoic acid m-Nitro-p-toluidine Alpha-naphthylaminem-nitroanilide of 2,3-

hydroxynaphthoic acid stands for diazotized and coupled to."

Among those less completely removed are As a general mode of procedure,the color may be completely or partly removed from 50 parts of cotton,linen, rayon, silk and wool or combinations of these in the forms ofcloth or yarn by treatment at 200 to 212 F. for 15 to 35 minutes in 1000to 2000 parts of water containing 1.5 to 5 parts of formamidine sulfinicacid and suflicient ammonia, or sodium or potassium carbonate to causethe liquor to react distinctly alkaline. To prevent the animal fibers,silk and wool, from being deleteriously afiected by the alkali, onlyammonia should be used, and in a quantity just sufiicient to cause theliquor to react with Brilliant Yellow paper.

Formamidine sulfinic acid is particularly useful for stripping acid anddirect dyestufis from wool or shoddy material. The product operates in aslightly alkaline bath at temperatures near the boil.

For the purpose of testing iormamidine sulfinic acid for this purpose, Ihad the following tests carried out:

Example 2 Samples of wool crepe were dyed with the following colors:

Per cent Pontamine Fast Yellow BBL (C. I. 814.) 2 Pontacyl Fast Blue R(C. I. 208) 2 Pontacyl Fast Blue 5R Conc. (C. I. 289) 2 Percentages areon weight of material.

The samples were then subjected to stripping with various strippingbaths according to the iollowing compositions:

Water 20.00

In all the above compositions the figures are based per unit part oftextile material. In all the above tests the fabric was treated with thesolution at 180 F. for /2 hour.

It was found that formamidine-sulfinic acid is superior to the SulioxiteS type of stripper for acid and direct colors, and reduces the fabricmore nearly to a white. This efiect was observed particularly in Tests(b), (c) and (d), as compared to Test (a) It will be understood that theabove examples are merely illustrative, and that the details of myprocess are susceptible of wide variation and modification within theskill of those engaged in this art.

I claim:

1. The process of stripping the color from textile material which hasbeen dyed with a color of the group consisting of vat and azoic colors,which comprises treating the fabric in an aqueous bath containingformamidine-sulfinic acid and alkali at a temperature near the boilingpoint of the solution.

2. The process of stripping azoic colors from cellulosic fiber, whichcomprises treating the fiber, at a temperature between 180 and 212 F.,in an aqueous bath containing from 0.1 to 1% by weight of formamidinesulfinic acid and sufficient alkali to give the liquor an alkalinereaction.

3. The process of stripping azoic colors from wool fiber, whichcomprises treating the fiber, at a temperature between 180 and 212 F.,in an aqueous bath containing from 0.1 to 1% of formamidine-sulfinicacid and just enough ammonia to give the liquor an alkaline reaction toBrilliant Yellow paper.

4. A process as in claim 1, the treatment being carried out in thefurther presence of a quaternary ammonium compound having an aliphaticradical which contains not less than 10 carbon atoms.

HERBERT AUGUST LUBS.

